MIPS: Octeon: Check all CCAs in cvmx_write_csr.

The current code only checks CCA of 0 when deciding if a dummy read is
needed.  Since the kernel can (and does) use other CCAs we need to
mask out the CCA bits from the address.  Since the address constant
now fits in 16 bits, there is an added benefit that smaller code is
generated.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>